It is important that utility workers when working in underground utility installations have an efficient, safe and reliable source of fresh air and heat. Underground utility installations can be cold, damp and contain foul air capable of causing the worker to lose consciousness. Existing rules require that the workers purge the underground utility installation before entering it. The portable ventilating heater of the present invention performs the dual functions of providing fresh air and heat. The blower is operable independent of the heater and, therefore, can be used to purge and continue to supply fresh air to an underground utility installation. After purging the installation, if it is desired to introduce heated air, the heater is activated also.